1. Technical Field
Embodiments of the present invention generally relate to a developing device, a process cartridge, and an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction machine having at least two of coping, printing, facsimile transmission, plotting, and scanning capabilities, that includes a developing device.
2. Description of the Background Art
Generally, image forming apparatuses include a developing device to develop latent images formed on a latent image bearer with developer. For example, there are two-component developing devices that employ two-component developer consisting essentially of toner particles and carrier particles. In two-component developing devices, a casing to contain developer includes an opening to partly expose the surface of a developer bearer (such as a developing roller), and the exposed surface of the developing roller faces the surface of the latent image bearer (such as a photoreceptor). A magnetic field generator provided inside the developing roller generates a magnetic field to generate a magnetic brush of developer on the developing roller, and the magnetic brush contacts the photoreceptor in a range where the developing roller faces the photoreceptor. Thus, toner is supplied to the latent image on the photoreceptor, developing it into a toner image.
In such a developing device, the magnetic field generator inside the developing roller does not extend to the outer ends in the axial direction, and the magnetic brush is not generated on the surface of the developing roller in areas adjacent to the outer ends (hereinafter “axial end portions”). If the amount of charge is insufficient, toner in the developing device is not adsorbed to carrier and floats. The floating toner can be transported by airflow generated by rotation of the developing roller and scatter outside from the opening. The scattering of toner can result in contamination inside the apparatus and substandard images.
The developing device further includes a developer regulator (such as a doctor blade) disposed upstream from the opening in the direction of rotation of the developing roller. In the area on the surface of the developing roller where the magnetic brush is formed (hereinafter “magnetic brush area”), the magnetic brush fills in clearance between the developer regulator and the surface of the developing roller. This prevents toner borne on the airflow from passing through a gap (i.e., a regulation gap) between the developer regulator and the surface of the developing roller, thus preventing the occurrence of toner scattering.
By contrast, since clearance is present in the axial end portions of the developing roller, where magnetic brush is not present, toner borne on the airflow passes through the regulation gap. Then, the toner is transported along the surface of the developing roller to the opening and can scatter outside from the axial end portions of the opening.
To inhibit scattering of toner from the axial end portion of the opening, there are configurations (such as JP-S60-010276-A, JP-S61-198260-A, JP-2006-145815-A, and JP-2005-321762-A) in which a lateral end cover constructed of flexible, elastic sheet is used to cover the area adjacent to the axial end of the developing roller from the side of the photoreceptor facing the developing roller in the opening.
Such configurations using the lateral end cover can inhibit toner transported through the regulation gap by airflow from colliding against the face of the lateral end cover on the side of the developing roller and scattering outside through the opening.
For example, JP-560-010276-A proposes a configuration in which the lateral end cover covers, in addition to the portion where the magnetic brush is not present on the surface of the developing roller, an area adjacent to the axial end of the magnetic brush area so that the lateral end cover covers the portion where the magnetic brush is not present on the surface of the developing roller to inhibit toner from scattering through the axial end portion of the opening.